1. CHAPTER 1 : MEASUREMENTS
SIGNIFICANT FIGURES AND
CALCULATIONS

2. Significant figures and calculations

3. Significant figures in a measurement include all of the digits that are known, plus one more
digit that is estimated.

4. Significant Figures •Any digit that is not zero is significant
2.234 kg 4 significant figures
•Zeros between non-zero digits are significant m 3 significant figures
• Leading zeros (to the left) are not significant L 1 significant figure.
g 3 significant figures
Trailing ( to the right) only count if there is a decimal in the number.
5.0 mg 2 significant figures.
50 mg 1 significant figure.

5. Two special situations have an unlimited number off Significant figures:
1.. Counted items
a) 23 people, or 425 thumbtacks
2 Exactly defined quantities
b) 60 minutes = 1 hour

6. Practice #1 How many significant figures in the following? 1.0070 m
5 sig figs
17.10 kg
4 sig figs
100,890 L
5 sig figs
3.29 x 103 s
3 sig figs cm
2 sig figs
3,200,000 mL
2 sig figs
5 dogs
unlimited
This is a
counted value

7. Rounding Calculated Answers
Decide how many significant figures are needed
Round to that many digits, counting from the left
Is the next digit less than 5? Drop it.
Next digit 5 or greater? Increase by 1
3.016 rounded to hundredths is 3.02
• rounded to hundredths is 3.01
• rounded to hundredths is 3.02
• rounded to hundredths is 3.04
• rounded to hundredths is 3.05

8. Addition and Subtraction
The answer should be rounded to the same number of decimal places as the least number of decimal places in the problem. Examples:
4.8
-3.965
1 decimal places
3 decimal places

9. Make the following have 3 sig figs:
762 M
14.334
10.44
10789
14.3
10.4
10800
8020
204

10. Multiplication and Division
Round the answer to the same number of significant figures as the least number
of significant figures in the problem.

11. Multiplication and Division: # sig figs in the result equals the number in the least precise measurement used in the calculation.
6.38 x 2.0 = (2 sig figs)

12. Addition and Subtraction: The number of decimal places in the result equals the number off decimal places in the least precise measurement.
= (3 sig figs)
= round off to 90.4
one significant figure after decimal point
= two significant figures after decimal point round off to 0.79

13. Scientific Notation

14. What is scientific Notation?
Scientific notation is a way of expressing really big numbers or really small numbers.
It is most often used in “scientific” calculations where the analysis must be very precise.

15. Why use scientific notation?
For very large and very small numbers, these numbers can expressed in a more concise form.
Numbers can be used in a computation with far greater ease.

16. Scientific notation consists of two parts:
A number between 1 and 10
A power of 10
N x 10x

17. Changing standard form to scientific notation.

18. EXAMPLE
= 5.5 x 106
We moved the decimal 6 places to the left.
A number between 1 and 10

19. EXAMPLE #2
Numbers less than 1 will have a negative exponent.
0.0075
= 7.5 x 10-3
We moved the decimal 3 places to the right.
A number between 1 and 10

20. EXAMPLE #3 CHANGE SCIENTIFIC NOTATION TO STANDARD FORM 2.35 x 108=
Standard form
Move the decimal 8 places to the right

21. EXAMPLE #4 9 x 10-5 = 9 x 0.000 01 = 0.000 09 Standard form
Move the decimal 5 places to the left

22. TRY THESE Express in scientific notation 1) 421.96 2) 0.04213) 4)

23. TRY THESE Change to Standard Form 1) 4.21 x 105 2) 0.06 x 103

24. To change standard form to scientific notation…
Place the decimal point so that there is one non-zero digit to the left of the decimal point.
Count the number of decimal places the decimal point has “moved” from the original number. This will be the exponent on the 10.

25. Continued…
If the original number was less than 1, then the exponent is negative. If the original number was greater than 1, then the exponent is positive.

26. Types of Errors
Random errors- the same error does not repeat every time.
• Blunders
• Human Error

27. Systematic Errors
– These are errors caused by the way in which the experiment was conducted. In other words, they are caused by flaws in equipment or experimental.
Can be discovered and corrected.

28. Examples:
You measure the mass of a ring three times using the same balance and get slightly different values: g, g, g. ( random error )
The meter stick that is used for measuring, has a millimetre worn off of the end therefore when measuring an object all measurements are off.
( systematic error )

29. Accuracy or Precision • Precision • Accuracy
Reproducibility of results
Several measurements afford the same
results
Is a measure of exactness
• Accuracy
How close a result is to the “true” value
Is a measure of rightness

30. Accuracy vs Precision π Accuracy Precision 3 NO 7.18281828 YES 3.14

31. Metric Conversions Ladder Method

32. How many jumps does it take?
Ladder Method 1 2 3
KILO 1000 Units
HECTO 100 Units
DEKA 10 Units
DECI 0.1 Unit
Meters Liters Grams
CENTI 0.01 Unit
MILLI Unit
How do you use the “ladder” method?
1st – Determine your starting point. 2nd – Count the “jumps” to your ending point. 3rd – Move the decimal the same number of jumps in the same direction.
4 km = _________ m
Starting Point
Ending Point
How many jumps does it take? 4. 1
__. 2
__. 3
__.
= 4000 m

33. Conversion Practice Try these conversions using the ladder method.
1000 mg = _______ g 1 L = _______ mL cm = _______ mm
14 km = _______ m 109 g = _______ kg 250 m = _______ km
Compare using <, >, or =.
56 cm m g mg

34. Metric Conversion Challenge
Write the correct abbreviation for each metric unit.
1) Kilogram _____ 4) Milliliter _____ 7) Kilometer _____
2) Meter _____ 5) Millimeter _____ 8) Centimeter _____
3) Gram _____ 6) Liter _____ 9) Milligram _____
Try these conversions, using the ladder method.
10) 2000 mg = _______ g 15) 5 L = _______ mL ) 16 cm = _______ mm
11) 104 km = _______ m 16) 198 g = _______ kg ) 2500 m = _______ km
12) 480 cm = _____ m 17) 75 mL = _____ L 22) 65 g = _____ mg
13) 5.6 kg = _____ g 18) 50 cm = _____ m 23) 6.3 cm = _____ mm
14) 8 mm = _____ cm 19) 5.6 m = _____ cm 24) 120 mg = _____ g